The I don't, I wouldn't, (or the reverse, I would, etc.) verses were used with good-lookin' woman, yaller gal, blondy woman, kinky-haided woman, jet-black, etc. There are many forms in addition to the one brought up by Roger.

Sometimes they were combined (from N. L. White):

I don't like a black gal, I tell you the reason why;
Her hair is so long and kinky, she'll break every comb I buy.
I don't like a yallow gal, I tell you the reason why;
Her neck is so long and stringy, I am afraid she'll never die.

Many forms and meters. Some came from the blackface minstrels and most were invented by the blacks themselves. One of the ancestors is "The Gal From the South," from the minstrels.

From Talley, Negro Folk Rhymes:
I wouldn't marry a black gal,
I'll tell you the reason why;
When she goes to comb dat head
De naps'll begin to fly

I wouldn't marry a black gal,
I'll tell you why I won't:
When she oughter wash her face-
We;;. I'll jes say she don't.

I wouldn' marry a black gal,
An' dis is why I say:
When you has her face around,
It never gets good day.